Remix education
B.S.CNursingpharmacy

Cellular Adaptation

Cellular Adaptation

Introduction

Homeostasis

• The “steady state” that cell exists in normally.
• An equilibrium of the cells with their environment for adequate function.
• When disturbed there is a predisposal for the onset of pathology.

Cells Adapt to Changes (Stimuli, Stressors)

Adaptations occur on a spectrum. Some are:
Helpful: hypertrophy or hyperplasia increase organ size so it can function better
More harm than good. Example: increased organ size requires more blood supply. If that is not available, organ becomes ischemic
Adaptation can involve:
• change in cell size or number
• change to different type of cell

On Application of Stress

img 20210324 1734559108390263775906661 Cellular Adaptation

NORMAL <—>ABNORMAL:

Cellular Adaptations

• Atrophy (brown atrophy)
• Hypertrophy

screenshot 2021 03 24 17 35 53 534 com8822386233820930092 Cellular Adaptation

Metaplasia: simple columnar to stratified squamous (lungs)
Dysplasia: some loss of control as in cervix

TYPES OF ADAPTATION

img 20210324 175147190668763970650558 Cellular Adaptation

ATROPHY

DEFINITION

SHRINKAGE OF CELLS

CAUSES

Physiologic
Due to decreased work load (e.g., decreased size of uterus following child birth, or disease)
Pathologic
• Starvation→Endocrine
• Ischaemic→Pressure
• Disuse→Idiopathic
• Neuropathic

Example of Atrophy

screenshot 2021 03 24 17 53 46 321 com6638702408688654638 Cellular Adaptation

HYPERTROPHY

DEFINITION

In the size of cells which results in enlargement of the organs , without any change in the no. of cells
It is mostly seen in cells that cannot divide, such as skeletal muscle (pumping iron), and cardiac muscle (hypertension).
These changes usually revert to normal if the cause is removed.
Hypertrophy is mediated by different mechanisms.
• Dividing cell →Hypertrophy + Hyperplasia
• Non-dividing cell → Hypertrophy

Causes of Hypertrophy

Physiologic
• Enlarged size of uterus in pregnancy
• Action of estrogenic hormones
Pathologic
• Hypertrophy of cardiac muscle

• Hypertrophy of Smooth muscle
• Hypertrophy of skeletal muscle
• Compensatory Hypertrophy

HYPERPLASIA

DEFINITION

Increased number of cells in an organ or tissue.
Hyperplasia may sometimes co-exist with hypertrophy.
Classification
Hyperplasia can be classified as:
Physiologic
hormonal (e.g., breast and uterus during pregnancy)
Compensatory
Degeneration of liver following partial hepatectomy. Various growth factors and interluekins are important in such hyperplasia.
Pathologic
excessive hormonal stimulation viral infection (papilloma viruses); neoplasms

Example of Hyperplasia

screenshot 2021 03 24 17 56 40 596 com8703926022058836037 Cellular Adaptation

screenshot 2021 03 24 18 07 07 032 com2578250644633008772 Cellular Adaptation

METAPLASIA

DEFINITION

Transformation or replacement of one adult cell type to another adult cell type (e.g., the change from columnar to squamous cells in respiratory tract, from squamous to columnar in Barrett esophagitis).
Metaplasia also occurs in mesenchymal tissue (e.g., formation of bone in skeletal muscle).
Metaplastic changes usually result from chronic irritation.
Metaplastic changes seem to precede the development of cancer, in some instances.

Types of Metaplasia

• Epithelial Metaplasia
o Squamous metaplasia
o Columnar metaplasia
• Mesenchymal Metaplasia
• Osseous metaplasia
• Cartilagenous metaplasia

EXAMPLES OF METAPLASIA

img 20210324 1810426829039181695602789 Cellular Adaptation

DYSPLASIA

The term “dysplasia” means “disordered cellular development”
It often accompanied by metaplasia & hyperplasia, thereby also referred as Atypical Hyperplaisa
• Short Duration → Reversible
• Long Duration → Carcinoma Cancer
It may occur due to Chronic Irritation or Prolonged inflammation.

Example of Dysplasia

screenshot 2021 03 24 18 12 10 211 com6408722543498794836 Cellular Adaptation

Key Facts

• Adaptable within physiological limits.
Heat Shock Proteins (HSPs): Can respond to injury by producing cell stree proteins.

• Demand met by Hypertrophy & Hyperplasia.
• Demand met by Atrophy.
Apoptosis : Cell loss can be achieved from Programmed cell death
• Tissue can adapt to demand by a change in differentiation known as Metaplasia.

screenshot 2021 03 24 18 14 34 925 com4022651668028633848 Cellular Adaptation

screenshot 2021 03 24 18 15 00 680 com1140156162544062956 Cellular Adaptation

Leave a review